Recently, scientific technologies rapidly progress around electronic industries, and particularly in semiconductor field, fine wiring and thinning of chips are made progress with a high integration of memory, whereby the mounting method is shifted to a surface-mounting. In an automated line for the surface mounting, there are problems that since packaged semiconductors suffer a sudden temperature change when leading wire is soldered, cracks occur in a resin molding product, or a boundary layer between the leading wires and the resin deteriorates, resulting in lowering a moisture resistance in semiconductor packages.
Therefore, as one of materials to be employed for the semiconductors, a curing agent for epoxy resins having an excellent heat resistance and moisture resistance has come to be used. For example, as a phenol-based curing agent having a moisture resistance, a dicyclopentadiene-modified phenol resin is proposed (Japanese Unexamined Patent Publication No. Sho 62-201922).
However, although the above-mentioned dicyclopentadiene-modified product is excellent in a moisture resistance, it has a defect that heat resistance cannot be satisfactorily obtained because of a low crosslinking density thereof.
Further, there is proposed a method (Japanese Unexamined Patent Publication No. Hei 7-17887) in which phenol resins obtained by a reaction of a specified diene or triene with phenols are used as a curing agent for epoxy resins. However, although heat resistance is improved in these methods, there are defects that the moisture resistance decrease in a cured product and the viscosity increases in an epoxy resin composition, with a result that workability lowers, high content filler loading becomes difficult, and cracks readily occur in a molded resin product due to increase in water absorption.